Films were silent until technology developed to include sound in the 1930s. The first fully composed film was King Kong in 1933.
The music to King Kong included leitmotifs and themes, not just background music like previous film compositions.
Music became important within films and was recognised by the Oscars in 1935 when the award Best Original Film was introduced.
John Williams (Star Wars, Jurrasic Park, Superman, Warhorse, War of the Worlds, Harry Potter...)
Hans Zimmer...(Gladiator, Dunkirk, Inception, Dune, Spiderman, Wonder Woman, Top Gun: Maverick_